Cellulosic textile materials are cross-linked with n-methylolacrylamide using one catalyst and a single reaction step

ABSTRACT

A METHOD FOR IMPARTING A DURABLE PRESS FINISH TO CELLULOSIC TEXTILE MATERIALS BY TREATING WITH N-METHYLOLACRYLAMIDE AND ZINC NITRATE AND HEATING TO CURE AND EFFECT CROSS-LINKING THE TEXTILE FINISH FOR PERFORMING THE METHOD AND THE RESULTING CELLULOSIC TEXTILE MATERIAL.

United States Patent Ofice Patented Feb. 9, 1971 9 Claims ABSTRACT OF THE DISCLOSURE A method for imparting a durable press finish to cellulosic textile materials by treating with N-methylolacrylamide and zinc nitrate and heating to cure and effect cross-linking, the textile finish for performing the method and the resulting cellulosic textile material.

TECHNICAL INFORMATION This invention relates to a durable press finish for cellulosic textile materials. More particularly, it relates to an aqueous textile finish containing N-methylolacrylamide and zinc nitrate. It also relates to a method of applying N-methylolacrylamide to cellulosic textile materials and to curing the N-methylolacrylamide on the textile material in the presence of Zinc nitrate. Furthermore, the invention relates to the cellulosic materials obtained by the method of this invention.

Methods are known for applying and curing N- methylolacrylamide on cellulosic textile materials using an acid-acting catalyst. All of the references, singly and/or collectively, teach that the product is an ether of cellulose of Formula I and that no cross-linking of the cellulose occurs.

The formation of the ether of Formula I is taught by U.S. Pat. Nos. 2,837,511 and 2,837,512. The first patent also teaches that cross-linking of the cellulose, resulting in improved crease resistance, can be obtained by treating the cellulose ether of Formula I with an alkaline material such as potassium hydroxide. According to the Pat. 2,837,511 and to a literature reference, J. of Appl. Polymer Sci., 5, 734 (1961), the cross-linking occurs by reaction at the double bond of Formula I with a hydroxyl group of cellulose when the alkali aftertreatmen-t is under went conditions. The product can be represented by Formula II.

If the alkali aftertreatment is under dry conditions, reaction of double bonds with cellulose hydroxyl groups is accompanied by ho mopolymerization to form an acrylic polymer which also provides cross-linking.

U.S. Pat. No. 3,125,405 and J. of Appl. Polymer Sci., 5, 734 (1961) teach that an ether of Formula I is obtained when N-methylolacrylamide is cured on cellulose in the presence of an acid-acting catalyst and that no cross-linking takes place. In Examples 1 and 2 of the patent the curing of N-methylolacrylamide on a cellulosic fabric using two conventional acid-acting catalysts re sulted in no improvement in the wrinkle recovery properties of the fabric. Cross-linking, accompanied by improvement in the wrinkle recovery properties, was accomplished by a second curing step using a free-radical initiator, such as a persulfate, to promote polymerization at the ethylenic double bond. Also, the cross-linked cellulose was obtained by the reverse procedure, namely, first curing in the presence of the free-radical initiator and then curing in the presence of the acid-acting catalyst. Furthermore, an acid-acting, free-radical initiator or a combination of free-radical initiator and acid-acting catalyst can be used to cause both types of reaction. In U.S. Pat. 3,125,406 there is further teaching of the 2-step method for obtaining cross-linking, using a free-radical initiator in the first curing step and an acid-acting catalyst, such as zinc nitrate, in the second step.

Another literature reference, Tex. Res. J. 35, 648 (1965), has disclosed the use of radiation to promote homopolymerization at the double bond of N-methylol acrylamide. This can be done on cellulosic textile materials. When such materials are then heated in the presence of an acid catalyst, cross-linking with the cellulose occurs and the wrinkle recovery of the fabric is increased. The same results can be obtained by the reverse procedure. N-methylolacrylamide is heated on a cellulosic fabric in the presence of an acid-acting catalyst and etherified cellulose is then irradiated to promote polymerization and cross-linking.

Therefore, it has been common knowledge and Well known to persons skilled in the art that in order to obtain a cross-linked cellulosic fabric having good Wrinkle recovery properties it is necessary to use (1) an acidacting catalyst to promote the reaction of the methylol group of N-methylolacrylamide with the cellulosic material and (2) a free-radical initiator, radiation or the hydroxyl ion to promote reaction of the double bond with cellulose or homopolymerization at the double bond.

The known methods for obtaining cross-linking of cellulose have disadvantages and the resulting cellulosic materials are often deficient in one or more properties. The materials and/or methods are exotic and are not those customarily employed by the textile finishing industry. The equipment and know-how are often lacking. Textile finishers prefer to use the manipulative steps with which they are acquainted and are equipped to perform, provided the resulting fabrics meet the requirements demanded by the trade.

It is therefore an object of this invention to provide a more simplified and direct method for obtaining a permanent press finish on cellulosic materials.

A further object is to provide a method for obtaining a direct one step curing of a finish comprising N-methylolacrylamide by means of the acid-acting catalyst.

These and other objects of the invention will become apparent as the description thereof proceeds.

The above objects may be achieved and the disadvantages of the prior art may be overcome by the use of the present invention.

It has been discovered that a textile finish containing N-methylolacrylamide can be cured in one step on cellulosic textile materials using a particular, although well known, acid-acting catalyst, namely zinc nitrate. That cross-linking and excellent durable press properties, including wrinkle resistance and crease retention, are obtained is especially surprising in view of the teaching of U.S. Pat. 2,837,512 that zinc chloride promotes the reaction only of the methylol group with cellulose to form the ether of Formula I. In addition, there is the general teaching of several references that acid-acting catalysts alone cannot cause cross-linking of cellulose with N- methylolacrylamide. Furthermore, U.S. Pat. 3,125,406 teaches the necessity of first using a free-radical initiator to accomplish polymerization at the ethylenic double bond before use of zinc nitrate to promote reaction of the methylol group with cellulosic hydroxyl groups. Thus, it

was not believed that zinc nitrate alone could promote both types of reaction and cause cross-linking of cellulose.

Moreover, as further evidence for the obtaining of cross-linking by the process of this invention, it has been observed that a second curing operation in the presence of a free-radical initiator does not provide a further increase in an already excellent wrinkle recovery. This clearly demonstrates that the reaction of the ethylenic double bond was already completed in the curing step with zinc nitrate.

The process of this invention can be carried out conveniently by impregnating a cellulosic textile material with a solution of N-methylolacrylamide and zinc nitrate and curing the finish on the textile material at an elevated temperature. If desired, the Zinc nitrate can be applied to the textile material before or after the N-methylolacrylamide, but it must be present when the material is heated to promote curing and cross-linking of the cellulose by N-methylolacrylamide.

N-methylolacrylamide is well known and aqueous solu tions of it are easily prepared by reacting acrylamide in aqueous medium with formaldehyde under alkaline conditions. The procedure is well known in the chemical literature.

It is convenient and practical to prepare and use an aqueous solution of N-methylolacrylamide; but, if desired, solutions or dispersions of N-methylolacrylamide in nonaqueous solvents may be used, such as for example, alcohols, ethers, ketones, and halogenated hydrocarbons.

The amount of N-methylolacrylamide applied to the textile material should be between 2% and 20%, preferably between 5% and based on the weight of the material.

As previously stated, it is practical to apply the zinc nitrate to the textile materials simultaneously with the N-methylolacrylamide from the same solution. However, the zinc nitrate can be applied, preferably from aqueous solution, before or after the N-methylolacrylamide.

The amount of zinc nitrate, calculated as the hexahydrate, used should be at least 0.5%, preferably between 1% and 2%, based on the weight of the textile material.

The cellulosic textile materials on which the finish is applied includes all the cellulosic fibers, such as cotton, rayon, linen, etc., and mixtures thereof; and blends of cellulosics and synthetic fibers, such as nylon, Dacron, Orlon, etc.

The textile materials can be in the form of woven or nonwoven fabrics, also as yarns, threads, webbing, batting, etc.

Conventional procedures, such as padding, dipping, spraying, etc., can be used to apply the finish to the textile materials.

After the N-methylolacrylamide and zinc nitrate have been applied to the textile material, the material is normally dried and heated at an elevated temperature to cause curing of the finish. By curing is meant the cross-linking of the cellulose with N-methylolacrylamide. Optionally, the drying and curing operations can be performed at the same time.

If the drying and curing steps are performed separately, the fabric can be dried at any convenient temperature, but short drying periods at 200230 F. are preferred.

For the curing operation, a temperature of between 300 and 375 F., preferably between 340 and 370 F., is satisfactory. A curing oven is normally used, but any conventional method for heating the textile material at the required temperature can be employed. The time required for complete curing can be readily determined and may be about 1.5 minutes at 350 F. for example.

The textile finish of this invention can contain other textile additives which do not interfere in the curing process. Such additives include softeners, wetting agents, brighteners, hand modifiers, water repellents and other textile fiinishing assistants well known in the art.

The cellulosic textile materials treated by the process 4 of this invention have excellent durable press and wash-and-wear properties. They exhibit good wrinkle recovery and crease retention qualities. They retain a crease well and show acceptable flat appearance. Also, the strength loss due to retained chlorine is very low.

In general, the process of this invention provides re sults that are equal or superior to those obtained by previous methods for finishing cellulosic materials with N- methylolacrylamide. Moreover, the process is much simpler and easier to control.

The following specific examples are given to illustrate the invention and are not intended to be limitative.

EXAMPLE I An aqueous pad bath was prepared containing 13% of N-methylolacrylamide and 1.56% of zinc nitrate hexahydrate. The pad bath was applied by standard padding procedure to x 80 cotton percale obtaining a wet pickup of 80%. The fabric, containing 10.4% of N-methylolacrylamide and 1.25% of zinc nitrate hexahydrate, was dried at 225 F. for two minutes, and the finish was then cured by heating the fabric at 350 F. for 1.5 minutes.

The wrinkle recoveries of the treated and untreated fabrics were measured, both dry and wet, by the AATCC Tentative Test Method 66-1959T.

Swatches of the treated and untreated fabrics were laundered six times in a home-style washing machine using hot water containing a synthetic detergent and a chlorine bleach (Clorox, a commercially available product). After the rinse cycles, the fabrics were dried.

The treated and untreated samples, both washed and unwashed, were tested for strength loss due to chlorine retention and scorching by AATCC Standard Test Method 921962.

The results of the tests are shown in Table I.

TABLE I Wrinkle recovery Strength loss due to W plus F, degrees ehlon'ne retention Unwashed, Washed, Dry Wet percent percent Fabric:

Treated 291 242 2. 7 14. 3 Untreated 211 129 0 1. 9

This example demonstrates the excellent wrinkle recovery properties, with low strength loss due to chlorine retention, that can be obtained by the process of this invention.

EXAMPL'E II were then heated in an oven at 320 F. for 8 minutes.

The fabrics were washed 5 times in a home-style washing machine, and the retention of the pressed-in creases was evaluated by the AATCC Tentative Test Method 88C- 1964T.

Additional swatches of the treated and untreated fabrics were pressed smooth and heated in an oven at 320 F. for 8 minutes. The fabrics were washed 5 times in a homestyle washing machine, and the smoothness of the fabrics was evaluated by AATCC Tentative Test Method 88A- 1964T, employing overhead lighting. The swatches were rated on a scale of 1 to 5, 5 representing the smoothest appearance and best retention of the original condition and 1 representing the poorest appearance and poorest retention of the original condition.

The results of the tests are shown in Table II.

TABLE II Grease Smoothretention ness Fabric:

Treated Excellcnt 3. 3 Untreated Poor 1.0

EXAMPLE III Six aqueous pad baths were prepared containing the amounts of N-methylolacrylamdie (NMA) and zinc nitrate hexahydrate shown in Table III. The pad baths were applied to 80 x 80 cotton percale obtaining an 80% wet pickup. The fabrics were dried at 225 F. for 2 minutes, and the finish was then cured at 350 F. for 1.5 minutes.

Tests were carried out on the treated and untreated fabrics as described in Example I to evaluate wrinkle recovery and strength loss due to chlorine retention. The results are shown in Table IV, Fabrics A to F corresponding with pad baths A to F, respectively.

TABLE IV Strength loss due to chlorine retention Unwashed, Washed,

Wrinkle recovery W plus F, degrees Dry Wet percent percent 276 222 3 31 F- 275 235 3 15 Untreated- 184 115 2 2 This example demonstrates the effectiveness of N- methylolacrylamide at two different levels as a wrinkle resistant finish when applied by the process of this invention. It also demonstrates the necessity of using an adequate amount of zinc nitrate in the curing process in order to obtain a low level of chlorine retention.

EXAMPLE IV TABLE V Crease Smoothretention ness Fabric:

A Excellent, 5. 3. 3 B .do 3. 5 C Good, 4 3.5 D do 3.0 E xcellent 3. 3 F. do 3. 8 Untreated Poor, 2 1. 3

EXAMPLE V An aqueous pad bath was prepared containing 13% of N-methylolacrylamide and 1.25% of zinc nitrate hexahydrate. The pad bath was applied by standard padding procedure to x 80 cotton percale obtaining a wet pickup of 80%. The fabric, containing 10.4% of N-methylolacrylamide and 1.0% of zinc nitrate hexahydrate, was dried at 225 F. for 2 minutes. A swatch of the dried fabric was then heated at 300 F. for 3 minutes. A second swatch was heated at 350 F. for 1.5 minutes. The tests described in Example I were carried out on the treated and untreated fabrics. The results are shown in Table VI.

TABLE VI Wrinkle recovery chlorine retention Unwashed, Washed, percent percent;

Wet

Fabric:

Dried only This example demonstrates the necessity of adequately curing the finish on the fabric in order to obtain the optimum physical properties.

EXAMPLE VI Four aqueous pad baths were prepared containing the amounts of N-methylolacrylamide and zinc nitrate hexahydrate shown in Table VII. The pad baths were applied to 80 x 80 cotton percale, obtaining an 80% wet pickup. The fabrics were dried at 225 F. for 2 minutes, and then heated at 350 F. for 1.5 minutes.

TABLE VII In pad bath Zn(N0a)2 -6 20, percent 0 n fabric Zn(NOa) z NMA, -6H 20 percent percent NMA, percent Pad bath:

F- lse m COMO! 2"!99 LHMEDKI 02000 WOONJ F999 roce cn The cured fabrics treated with Pad Baths B and C 'were then impregnated with a 0.5% aqueous solution TABLE VIII Wrinkle recovery W plus F, degrees Dry Wet Strength loss due to chlorine retention Washed Unwashed Fabric:

wa mop-av D Untreated This example demonstrates that no further wrinkle recovery is obtained by a second curing operation using a free-radical initiator, indicating that the curing step rvith zinc nitrate has completely cross-linked the celluose.

While certain specific emodiments and preferred modes of practice of the invention have been set forth, it will be understood that this is solely for illustration, and that various changes and modifications may be made without departing from the spirit of the disclosure or the scope of the appended claims.

I claim:

1. A method for imparting a durable press finish to a cellulosic textile material consisting of the steps of impregnating the textile material with N-methylolacrylamide and zinc nitrate, and heating the impregnated textile material to elfect cross-linking of the cellulose by the N-methylolacrylamide.

2. The method of claim 1 wherein the amount of N- methylolacrylamide is from about 2 to 20 percent based on the weight of the material.

3. The method of claim 1 wherein the amount of N- methylolacrylamide is from about 5 to 10 percent based on the weight of the material.

4. The method of claim 1 wherein the amount of zinc nitrate is at least 0.5 percent based on the weight of the textile material.

5. The method of claim 1 wherein the amount of zinc nitrate is at least between about 1 and 2 percent based on the weight of the textile material.

6. The method of claim 1 wherein said cellulosic material is cotton.

7. The method of claim 1 wherein said heating is 8 performed at temperatures between about 300 and 375 F. for sufiicient time to effect said cross-linking.

8. The method of claim 1 wherein said heating is performed at temperatures between about 340 F. and 370 F. for sufi'lcient time to efiect said cross-linking.

9. A cellulosic textile material obtained by the process of claim 1.

References Cited FOREIGN PATENTS 1,383,268 11/1964- France 8ll6.3

GEORGE F. LESMES, Primary Examiner I. CANNON, Assistant Examiner US. Cl. X.R. 8-120, 115.7 

